Control apparatus



y 1958 w. SCHAELCHLIN ETAL 2,836,074

CONTROL APPARATUS Original Filed June 18, 1952 4 sheets sheet 1 1 vr-iEh m [42b 4 -111] m a! J 1 i F|g.2.

M To Load A SC I I INVENTORS Walter Schoelchlin RE 5 L- m; ---cS-MongYClorenceE-Gory.

F ig.|. ATTORNEY 4 Sheets-Sheet 2 W. SCHAELCHLIN ETAL CONTROL APPARATUSINVENTORS Welter Schoelchlin and Clarence E. G0

ATTORNEY Fig.3.

May 27, 1958 Original Filed June 18, 1952 May 27, 1958 W. SCHAELCHLIN ETAL CONTROL APPARATUS 4 Sheets-Sheet 5 Original Filed June 18, 1952 y 7,1958 w. SCHAELCHLIN EIAL 2,836,074

CONTROL APPARATUS 4 Sheets-Sheet 4 Original Filed June 18, 1952 Fig. 6

Fig.5.

Chain Drive from Motor M to Cone Pulley I United States Patent CONTROLAPPARATUS Walter Schaelchlin and Clarence E. Gary, Buffalo, N. Y.,assignors to Viestinghouse Electric Corporation, East Pittsburgh, Pa, acorporation of Pennsylvania Original application dune 18, 1952, SerialNo. 294,149. Divided and this application September 15, 1953, Serial No.380,194

Claims. (Cl. 74-2395) This invention relates generally to mechanicaldrives and more in particular, to such drives which are adaptable forcontrolling the relative positions or the relative speeds of a pair ofmovable members.

' This application is a division of a copending appli cation of theSchaelchlin et al., Serial No. 294,149, filed June 18, 1952, entitled,Control Apparatus, and assigned to the assignee of this invention.

' Applications of the type generally referred to hereinabove are found,for example, in the control of the separate sections of a paper mill. insuch an application it is necessary in some instances to control therelative speeds of the stands to maintain the proper relationshipbetween the peripheral speeds of the rolls and in other instances it isnecessary to maintain a fixed angular position relationship between therolls of the respective stands. In such a drive a reference controlquantity is utilized as a basis for speed or position regulation. Thisquantity is usually differentially compared with a quantitycorresponding to the speed or position of a machine driving a givenstandin order to obtain an error quantity indicative of the controlwhich is required to bring the given machine into position or speedcorrespondence with the reference quantity.

In many such applications mechanical types of differentials may beutilized to obtain the error quantity and in order to achieve a degreeof drive flexibility in situations, for example, where the speeds of thesuccessive stands may not be identical, it is desirable to provide aform of variable speed device between the machine driving a given standand one input to the differential associated with and driven by thatparticular machine. Arrangements of this type are frequently cumbersomeand expensive to build and if not properly designed, may require toomuch maintenance service.

Accordingly, it is one object of this invention to provide a unitarymechanical drive involving a variable speed input to one side of adifferential.

Another object of this invention is to provide a drive of the characterreferred to which is simple with respect to operational requirements andpositive in operation.

A further object of this invention is to provide a variable speeddiiferential drive of a compact nature.

More specifically stated with respect to the preceding object, it is anobject of this invention to provide a variable speed cone pulley drivefor one side of a differential unit wherein the differential unit ismounted completely within a hollow end of one of the cone pulleys.

In sectionalized mill drives provision must be made for obtaining anadjustable amount of draw between the respective mill stands. Theapparatus herein generally described embodying the variable speed conepulley drive affords adjustment of the amount of draw between the millsections by means of adjustment of the belt of the cone pulley drivealong the cone pulleys to vary the drive ratio from the driving/to thedriven pulley. The

2,835,674 Patented May 27, 1958 setting of the draw adjustment fornormal operation, during which the web is being fed through therespective sections of the mill, is frequently not satisfactory for athreading operation when a new web is being threaded through the mill.The draw may be varied by manipulating the mechanism which drives thebelt shifter carriage to vary the draw as required during the threadingoperation, whereafter during continued operation this same mechanism maybe further adjusted to move the belt shifter carriage to obtain therequired draw for continued mill operation. In many respects thisadjustment is unwieldy.

Accordingly, it is a further object of this invention to provide avariable speed drive of the character referred to wherein provision ismade for incremental adjustment of the belt shifter with respect to thebelt shifter carriage to obtain small adjustments of the relative speedsof the cone pulleys Without moving the belt carriage.

The foregoing statements are merely illustrative of the various aims andobjects of this invention. Other objects and advantages will becomeapparent upon a study of the following disclosure when considered inconjunction with the accompanying drawings, in which:

Fig. l is a block diagram illustrating an application of the presentinvention;

Fig. 2 is an end view fragmentarily in section of a mechanical driveembodying the principles of this inventic-n;

Fig. 3 is a longitudinal sectional view taken approximately on the lineHIT-III of Fig. 2; V

Fig. 4 is a sectional view taken approximately on line iV--lV of Fig. 2

Fig. 5 is a plan view of the mechanical drive of Figs. 2 and 3; and

Fig. 6 is an elevational view taken along the line VI-VI of Fig. 5 toshow the belt change drive mechanism.

Fig. 1 illustrates a control of a single motor designated by the block Mutilized to drive a load such as one section of a mill. The speed ofthis motor is compared with the speed of a constant speed motor CSMwhich drives one side of a difierential designated D6. The other side ofthis differential is driven by a speed changer designated SC which inturn is driven by the motor which is to be controlled. The speed changerSC permits varying the speed of the motor M with respect to the constantspeed motor CSM by providing a step-up or reduction in the speed atwhich the associated input of the differential D8 is driven. The outputof the differential in angular position at any instant with respect to agiven reference angular position is an indication of a difference inspeeds between the motor M and the constant speed motor. This angularposition shift is detected by a position error detector designated E,the output of which may be applied through suitable electric amplifyingmeans A to the motor M to control the motor speed as required. A ratesignal may be introduced at this point by means of a rate of errordetector RE which, for example, may be responsive to the rate of changeof electric output of the position error detector E and its outpututilized to further control the amplifying means A. A control of asecond section of the mill may be obtained witha control correspondingto that illustrated in Fig. 1 and having as its reference the mechanicaloutput of the constant speed motor CSM or a corresponding motorenergized from the same source as the illustrated constant speed motor.The draw between these twosections may be adjusted by one or both of therespective speed changers in such a system to control the amount ofsag-back in the web between the respective sections.

, The details of the mechanical drive schematically illustrated in Fig.1 appear in Figs. 2, 3 and 4 wherein the speed changer SC, involving apair of cone pulleys 1 and 2 connected by a belt3, the differential gearDG the constant speed motor CSM and the position error detector E'aremounted upon a common support or housing-generally designated 4. Thishousing is fabricated of a plurality of angle sections 5 and coverplates 6 of ,a dimension and configuration to completely enclose thegenerally designated items.

The belt 3 is engaged by a belt shifter assembly generally designated 7disposed between the cone pulleys which is. provided to adjust the belt3 axially of the cone pulleys to .provide' a variation in the driveratio there between. Thusdepending upon the position of the belt 3 alongthe respective conepulleys 1 and 2, the cone pulley 2; which is thedriven pulley, will be operating at some speed either equal to, greaterthan or less, than the cone pulley 2 about the hollowspindle 8 aredesignated 10"and 11 and are mounted at axiallyspaced points along'thehollow spindle 8.

V v One ofthe input shafts to the differential D6 is concentricallyjournalled within the hollow spindle 8. This differential input shaft isdesignated 12. The left end of this input shaft is connected by a geartrain comprising gears 13, 14 and 15 tow-the constant speed motor CSM,which is mounted to the upper end of the bracket 9. 'Thus' input shaft12 is driven at a constant speed V by the constant speed motor.

The illustrated differential is assembled of a plurality of spur gears.The sun gear 16 representing one point .of input tothe differential unitis secured .to the right end of the differential input shaft 12. Thesecond input point of this drive is represented in theinternally toothedring gear 17 which is securely mounted against a shoulder 18 formedintegrallywithin the cone pulley 2; This secure mounting may beachievedby means of screws 19 extending through clearance holes in the ring gearand extending intosuitable tapped holes in the shoulder 18.; A pluralityof planet pinions 20 only one of which is illustrated are mounted incircumferen- 7 tially spaced relationship upon a'planet carrier 21 whichpositions the planet'pinions between and in mesh with pulley 29 isdetermined by the transmitting capacity of the friction clutch;

Pulley 29 is connected by a belt 33 to a pulley 34 driving apotentiometer type of rheostat .such as deslg- V nated E. It will beappreciated that such a position error detector may also be a suitablywound rotor, wound stator inductively coupled device wherein the voltageinduced in the secondary of such a device varies as a function of theangular displacement of the rotor of the device from a' givenangularposition. Other suitable devices may obviously be utilized as thepositionerror detecting means. Pulleys 29 and 34 are cluster pulleysutilizing a V-belt drive 33 and provide an interesting feature of thedrive consisting in the adjustable gain or amplification of the.regulator obtained .by the use of such pulleys. It is always desirableto operate the error detecting device at maximumfspeed so as to obtainquick response of the system; however, in'certain cases where theinertia of the section being regulated is high it is desirable to reducethe speed of movement of the error detector and this arrangement makesit relatively easy to do so by simply shifting the belt 33 to 'obtainthe desired drive rate. This can be done by an inexperienced operator. 7

Although the friction clutchconnected in the drive between, differentialoutput shaft 22 and the error de-.

tector E has been indicated at the pulley 29, it will be appreciatedthat this connection'may be provided with equal facility at the pulley34.. The primary purpose of a connection such as this is to provide ameans forslipping this drive with respect to the input-to the errordetector which usually is limited in angular movement the sun gear-16and the internal ring gear 17. The.

planet carrier 21 is secured to the differential output shaft 22journalled in bearings 23 in a bearing housing 24 forming a part of thecone pulley end plate 25. A

'tapped'holes in the end ofcone pulley 2.

Differential output shaft 22 is frictionally connected to 'a pulley'29by means of a friction type of clutch generally designated C1. Pulley 29represents the input to a drive'such as G1 between the differentialoutputishaft and the. error detector E. This friction clutch isconventional in principle and comprises a plurality of spring biasedfriction plates 30 which are alternately connected to a .clutch' member31 secured'to differential output shaft 22 and a sleeve 32 rotatablymounted about the output shaft and secured .to the cone pulley 29.Withthis' ar: rangement the magnitude of torque deliverable to the bymechanical stops. Thussuificient torque is achieved in the drive todrivethe movable element of the error detector atrates of accelerationat least equal to the maximum acceleration rates required but when there:

tatingelement ofthe detector encounters the stops therein the frictionconnection permits the drive to slip to avoid. damage. to the errordetector. -By movement of the belt shifter assembly or carriage axiallyof the conev pulleys the drive ratio between the cone pulleys is varied.To this end the belt shifter carriage is mounted for axial movementalong the length of the cone pulleys. carriage 7 is illustrated in Fig.4. This section is taken through the carriage along an axis parallel totheaxes of the cone pulleys as illustrated by section lines IV-IV ofFig. 2. This'belt shifter carriage comprises a body portion having endplates'35. and 36. These end plates are secured in spaced relation asindicated by a pairof spacers 37 appearing only in Fig. 2 .and a spacer38 which appears in both Fig. 2 and Fig. 4.. Spacer 38 is of tubularconfiguration having a hole 39 extending theretapped at 40 to receivescrews41 which extend through respective end plates '35 and 36 andthread into the tapped end sections to secure the assembly.

The belt shifter 42 comprises amagnetizable plate 7 43, theconfiguration of'which is best seen in dotted outline in Fig. 2. Theends of this plate project above and below the carriage respectively andhave mounted thereon respective yokes .42aand 4212 which engage theopposite sides of belt 3. Plate 43.is provided with a slotextending'through one side thereof having arcuate side portions 45 aboutthe geometric center of. the plate. A

sleeve bearing 46 is fitted through the arcuate side portions of thisslot and'securedto the magnetizable plate 43 by any suitable means suchas welding or brazing.

Sleeve 46 is slidably mounted about the tubularspacer and 15 securedagainst rotation about the sleeve by means of a pin 47 which movesthrough slotted openings 48 at diametrically opposite in the walls ofthe tubular spacer and is secured inlsleeve 46. vProvision is made forcentrally positioning the belt shifter 42'substantially centrally of thecarriage along the tubular spacer. Speci- A sectional view of the beltshifter V fically this provision includes a shoulder 49 which is formedcentrally within the tubular spacer. Plungers 50 and 51 are slidablyfitted into the tubular spacer on opposite sides of shoulder 49 and abutthe shoulder. These plungers are maintained in the position indicated byrespective compression springs 52 and 53 which are compressed betweenthe respective plungers 50 and 51 and the screws 41 which are threadedinto the ends of the tubular spacer. in the position illustrated the pin47 is biased to a central position along the tubular spacer and whendisplaced to one side or the other, it must move against the force ofthe respective springs which tend also to move the pin and hence, thebelt shifter to its central position. Consequently, this belt shifter isresiliently secured in a central position on the belt shifter carriage.The pin 47 is sufficiently small in dimension between the confrontingfaces of plungers 50 and 51 to slightly clear the plunger faces when theplungers abut the shoulder 45 Thus, a strong centering bias is appliedto the pin 47 and the spring load of the inactive spring, when the pin47 is displaced from central position, is carried by the shoulder 49.

The plate 43 is formed of magnetic material and constitutes the armaturefor a pair of oppositely disposed electromagnets 54 and 55'. Therespective electromagnets comprise magnetizing coils 56 and 57 which areof substantially annular configuration and are disposed about the sleeve36 against the respective inner faces of end plates 35 and 36. Themagnetic circuit of the respective magnets include respective annularmembers 58 and 59 which are disposed about the respective coils 56 and57. The ends of these annular members adjacent the respective end platesare fitted respectively into a suitable groove which is milled in theinner face of each plate and secured in this position by means ofwelding or brazing. The remaining ends of these annular members confrontopposite sides of the armature plate 43 and are spaced therefrom in anamount to provide limited movement of the belt shifter with respect tothe carriage by magnetic attraction in either direction from thecentrally illustrated position. Small angle sections or rings of angularcross-section designated 60 and 61 are respectively fitted over the endsof respective members 53 and 59 which confront the opposite sides of thearmature plate to prevent sticking of the armature plate to the polefaces constituted by the ends of the respective annular members.

The belt shifter carriage is mounted upon a pair of bars or rods which.are supported between the ends of the housing 4 in positions parallelingthe axis of the cone pulleys and 2. The lower rod 62, in Fig. 4 and alsoFig. 2, is secured in fixed relation with respect to the housing andforms a guide over which slots 63 in the bottom edges of the respectiveend plates 35 and 36 are fitted so that the carriage may slidetherealong. The upper rod 64- is threaded along its length and isrotatably mounted in suitable bearings not shown in the ends of housing4. The lrcaded rod 64 engages nuts 65 and 66 which are secured inrespective end plates 35 and 36 adjacent the tpper ends of these plates.Back-lash is taken out of the threaded mechanical connection by means ofa comression spring 67 which is compressed between respective nuts 65and 66. This compression spring biases the nut 65 and do away from oneanother an amount sufficient to securely engage the faces of the threadsof the nuts with the faces of the threads of the threaded bar or shaftin accomplishing this, nut 66 is provided with a square or rectangularshank 66a which slidably fits through a square hole 661) in plate 36.Since the thread faces thus engaged are oppositely disposed, rotation ofthe bar in either direction results in positive movement without loss ofmotion of the belt shifter carriage, in one direction or the reverse.The means for rotating the threaded shaft 64 may be a suitable crank orknob 68,

shown in dotldash outline in vFig. 2 only, secured to the. end of thethreaded shaft in a position projecting beyond the boundaries of housing4 so that it may be easily reached. Alternatively, this shaft may bemotor operated from a remote point. For this purpose a draw adjustmentmotor DM, connected to the end of threaded rod 64 opposite the crank 68,by means of chain and sprocket drive 70, may be employed, see Fig. 6.

With the structural arrangement herein described, the angular rate ofthe output shaft of the difierential is an indication of the differencein speed between the cone pulley 2 which is driven by the cone pulley 1and the shaft 12. which later represents the other input connection ofthe differential. The angular position of the differential output shaftat any instant with respect to a given ref l ence position is anindication in a change in angular relation between cone pulley 2 and theshaft 12. The electric intelligence developed by the position errordetector or other suitable device as shown in Fig. 1 controls the motorM in such a way as to match the speed of cone pulley 2 with the shaft12. In effect, the drive herein described is basically a positionregulator comparing actual revolutions of the reference represented inshaft 12 with a speed represented in revolutions of cone pulley 2 whichis a function of the speed of the member or motor being controlled. Asystem incorporating such a drive therefore, synchronizes the angularposition of cone pulley 2 with that of shaft 12 tending always to insuremaximum accuracy of regulation.

The details whereby adjustment of the draw of a particular section ofthe mill may be achieved are now more readily appreciated. Theadjustment of drive ratio provided by the belt shifter carriage driveaffords the desired control of the motor driving a particular section ofthe mill to obtain satisfactory mill operation.

At such times, however, as it is found desirable to affect momentarychange in the draw of a section of a mill in order to take up slackaccumulations in the Web or to introduce a slight amount of slack in theWeb, the adjustment may be conveniently made, without changing the drawsetting for the particular section, through the control aiforded by theelectromagnets which provide sll st adjustment of the belt shifter fromits mid position I etween the two electromagnets.

These elcctromagnets may be connected in series with respectivepush-buttons PB and FBI. across a supply of electrical energy EV. Thus,selective energization of the magnets by operation of the respectivepush-buttons will permit a small adjustment of the belt shifter withrespect to the belt shifter carriage to thereby provide a momentaryadjustment of section draw.

Although but one embodiment of this invention has been illustrated inthe accompanying drawing and but one application of this invention hasbeen indicated, it will be appreciated that numerous other applicationsare feasible and that numerous variations in the details of componentsand the organization of the respective components may be made by thoseskilled in the art without departing from the spirit and scope of thisinvention. Accordingly, it is intended that the foregoing disclosure andthe illustrations in the drawings are to be considered only asillustrative of the principles of this invention and not interpreted ina limiting sense.

We claim as our invention:

1. A variable speed differential comprising, a support, a driving conepulley rotatably mounted on said support, motor means for driving saiddriving cone pulley,.a hole low shaft fixed on said support with theaxis thereof parallel to the axis of the first cone pulley, a drivencone pulley, said driven cone pulley having a hollew end, bearing meansrotatably mounting said driven cone pulley about said hollow shaft, abelt connecting said cone pulleys, a drive shaft rotatably mounted on Sid hollow haf n p oj ct n at e end Out of said hollow sha t into, thehollow end of said second conepull ey, means for driving said driveshaft, a spur gear secured to said one'end of said drive shaft,aninternally toothed ring gearseciired within the hollow end of saidsecond cone pulley in a plane defined by said spur gear, a rotatablymounted planet gear carrier, at least one planet gear meshing with bothsaid ring gear and said spur gear and rotatably mounted on said; planetgear'carrier, and means responsive to angular movement of said planetgear carrier for indicating the diiference in speed between said drivenpulley and said drive shaft.

, t 2; A variable speeddifferential comprising a suPP OIt, a drivingcone pulley rotatably mounted on said support,

meansfor driving said driving cone pulley, a hollow shaft fixed on saidsupport, a driven cone pulley having a hollow end, bearing meansrotatably mounting said driven cone pulley about said hollow shaft,abelt connecting said cone pullcys,'belt shifter' means engaging saidbelt for moving said belt along said pulleys, a drive shaftrotao ablymounted in said hollow, shaftand projecting at one end thereof from saidhollow shaft into the hollow end of said hollow cone pulley, means fordriving said drive shaft, aspur gear secured to said one end of saiddrive shaft, an internally toothed ring gear secured within said,

hollow end of said hollow cone pulley in a plane defined by said spurgear, a planet carrier, an end plate secured over said hollow end ofsaid hollow cone pulley, bearing means rotatably mounting said planetcarrier in said end plate in a position coaxially of said' drive shaft,at least one planet gear rotatably mounted on said planet carrierbetween and meshing with both saidring gear and said spur gear, andmeans responsive to angular movement of Qsaid planet carrier forindicating the difference in speed between said driven pulley and saiddrive shaft.

3.;Apparatus for indicating a difference in angular position between tworot atable' bodies comprising, a' support, a driving cone pulleyrotatably mountd on said supportand adapted to be driven by one of saidbodies, a hollow shaft mounted on said support with the axis thereofsubstantially parallel to the axis of said first cone pulley, a drivencone pulley having a hollow end, bearing means 7 V rotatably mountingsaid driven cone pulley about said hollow shaft, a belt connecting saidcone pulleys, a drive shaft rotatably mounted in said hollow shaft andprojecting therefrom at one end into said hollow end of said driven conepulley, said drive shaft being driven by the other of said bodies, aspur gear secured to said one end of said drive shaft, an internallytoothed ring gear dis- .posedwithin said hollow end of said driven conepulley substantially in theplane, defined by said spur gear, a planetcarrier rotatably mounted coaxiallyof said drive shaft, at least oneplanet gear rotatably mounted on said planet carrier and meshing withboth said ring gear and said spur gear, an electrical pickolf devicehaving a rotatable member, means including a slip'clutch connectingsaid, planet'carrier with said rotatable member of said i 7 electricalpickoff, and means-responsive to'the electrical output of saidelectrical picltoif for controlling one of said bodies. a

tion between two rotatable bodies comprising, a support a first conepulley rotatably mounted on said support and adapted to be driven by oneof said bodies, ahollow. shaft mounted on said support with the axisthereof substantially' parallel .to the axis of said first cone pulley,a hollow cone pulley, bearing means rotatably mounting said 1101- lowcone pulley about said hollow shaft, abelt connecting'said cone pulleys,a drive shaft rotatably mounted in said hollow shaft and projectingtherefrom at one end into said hollow c o'ne pulley, a spur gear securedto said oneend of said drive shaft, an internally toothed ring geardisposed within said hollow cone pulley substantially in the'planedefined by said spur gear, a planet carrier.

rotatably :moun t'ed coaxially of said drive shaft, at least one planetgear rotatably mounted on said planet carrier and meshing with both saidring gear and said spur gear,

an electrical pickoff device having a rotatable memben and a variablespeed drive connecting said planet carrier with said rotatable member ofsaid electrical pickofi.

'5. Apparatus for indicating a difierence in angularposition between tworotatable bodies comprising, a support, a first'cone pulley rotatablymounted on .said support and adapted to be driven by one of said bodies,a

hollow shaftmounted on said support with the axial thereof substantiallyparallel to the axis of said firstcone pulley, a hollow cone pulley,bearing means rotatably mounting said hollow cone pulley about saidhollow shaft,

a belt connecting said. cone pulleys, a drive shaft rotatsubstantiallyin the plane defined by said spur gear, a planet carrier rotatablymounted coaxially of said drive shaft, at least one planet gearrotatably mounted on sm'd' planet carrier and meshing with both saidring gear and said spur gear, an electrical pickoff device having arotatable member, means includingaa slip clutch'connecting V V ember ofsaid electrical pickoif, a variable speed drive connecting saidsaidplanet carrier with said rotatable planet carrier with said rotatablemember of said electrical n o V V 4. Apparatus for indicating adifference in angular posir picked, and a slip clutch connected withsaid variable speed drive. V 6. Apparatus for indicating a difference inangular position between two rotatable bodies comprising, a sup port, afirst cone pulley rotatably mounted on said support and adapted to bedriven by one of said bodies, a hollow shaft mounted on said supportwith the axis toothed ring gear disposed within said hollow cone pulleysubstantially in the plane defined by said spur gear, a planet carrierrotatably mounted coaxially of said drive shaft, at least one planetgear rotatably mounted onsaid planet carrier and meshing with both saidring gear and said spur gear, an electrical pickofi device having arotatable member, a pulley cluster connected to said rotatable member ofsaid electrical pickoff, a pulley cluster connected' to said planetcarrier, and a belt connectingsaid pulley clusters, said belt beingadjustable between corresponding pulleys of said respective pulleyclusters to vary the drive ratio therebetween. 7 e a 7. Apparatus forindicating a difierence in angular position between two rotatable bodiescomprising, a sup-f port, a first cone pulley rotatably mounted on saidsupport and adapted to be driven by one of said bodies, a

hollowshaft mounted on said support with the axis thereof substantiallyparallel to the axis of said first cone pulley, a hollow cone pulley,bearing means rotatably mounting said hollow cone pulley about saidhollow shaft, 7 a belt connecting said ,cone pulleys,- a drive shaftrotat- V ably mounted in said hollow shaft and projecting therefrom atone end into said hollow cone pulley, a spur, gear'secured to said oneend of said drive shaft, an indrive shaft, at least one planet gearrotatably mounted on said planet carrier-and nieshingwith both said ringgear and said spur gear, an electrical pickoif device having a rotatableinput shaft, a pulley cluster on said shaft of said electricallpickofi,a pulley clustenon said shaftof said planet carrier, a belt connectingcorresponding pulleys asaaova 9 of said pulley clusters, said belt beingadjustable between corresponding pulleys of said respective clusters tovary the drive ratio therebetween, and a slip clutch connecting onepulley cluster to the shaft therefor.

8. Apparatus for indicating a difference in angular position between tworotatable bodies comprising, a support, a first cone pulley rotatablymounted on said support and adapted to be driven by one of said bodies,a hollow shaft mounted on said support with the axis thereofsubstantially parallel to the axis of said first cone pulley, a hollowcone pulley, bearing means rotatably mounting said hollow cone pulleyabout said hollow shaft, a belt cmrnecting said cone pulleys, a driveshaft rotatably mounted in said hollow shaft and projecting therefrom atone end into said hollow cone pulley, a spur gear secured to said oneend of said drive shaft, an internally toothed ring gear disposed witmnsaid hollow cone pulley substantially in the plane defined by said spurgear, a planet carrier having a shaft, bearing means rotatably mountingsaid planet carrier shaft coaxially of said drive shaft, at least oneplanet gemrotatably mounted on said planet carrier and meshing with bothsaid ring gear and said spur gear, an electrical pickoff device having arotatable inputshaft, a pulley cluster on said shaft of said electricalpickoff, a pulley cluster on said shaft of said planet carrier, a beltconnecting corresponding pulleys of said pulley clusters, said beltbeing ad ustable between corresponding pulleys of said respectiveclusters to vary the drive ratio t erebetween, a slip clutch connectingone pulley cluster to the shaft therefor, said slip clutch comprising aplurality of engaged friction plates alternately connected to the pulleycluster and the shaft therefor, means supporting said friction platesfor relative axial movement and spring means axially biasing said platesinto frictional engagement.

-9. Apparatus for indicating a difference in angular position betweentwo rotatable bodies comprising, a support, a first cone pulleyrotatably mounted on said support and adapted to be driven by one ofsaid bodies, a hollow shaft mounted on said support with the axisthereof substantially parallel to the axis of said first cone pulley, ahollow cone pulley, bearing means rotatably mounting said hollow conepulley about said hollow shaft, a belt connecting said cone pulleys, adrive shaft rotatably mounted in said hollow shaft and projectingtherefrom at one end into said hollow cone pulley, a spur gear securedto said one end of said drive shaft, an internally toothed ring geardisposed within said hollow cone pulley substantially in the planedefined by said spur gear, an end plate mounted on the end of saidhollow cone pulley adjacent to said ring gear, a planet carrier having ashaft, bearing means in said end plate rotatably mounting said shaft ofsaid planet carrier coaxially of said drive shaft, said shaft of saidplanet carrier extending through said end plate, at least one planetgear rotatably mounted on said planet carrier in a position meshing withboth said ring gear and said spur gear, an electrical pickoff devicehaving an input shaft, and drive means connecting said planet carriershaft with said input shaft of said electrical pickolf.

10. Apparatus for indicating a difierence in angular position betweentwo rotatable bodies comprising, a support, a first cone pulleyrotatably mounted on said support and adapted to be driven by one ofsaid bodies, a hollow shaft mounted on said support with the axisthereof substantially parallel to the axis of said first cone pulley, ahollow cone pulley, bearing means rotatably mounting said hollow conepulley about said hollow shaft, a belt connecting said cone pulleys, adrive shaft rotatably mounted in said hollow shaft and projectingtherefrom at one end into said hollow cone pulley, a spur gear securedto said one end of said drive shaft, an internally toothed ring geardisposed within said hollow cone pulley substantially in the planedefined by said spur gear, an end plate mounted on the end of saidhollow cone pulley adjacentto said ring gear, a planet carrier having ashaft, bearing means in said end plate rotatably mounting said shaft ofsaid planet carrier coaxially of said drive shaft, said shaft of saidplanet carrier extending through said end plate, at least one planetgear rotatably mounted on said planet carrier in a position meshing withboth said ring gear and said spur gear, an electrical pickolf devicehaving an input shaft, and means including a variable speed driveconnecting said planet carrier shaft to said input shaft of saidelectrical picked.

11. Apparatus for indicating a difference in angular position betweentwo rotatable bodies comprising, a sup port, a first cone pulleyrotatably mounted on said support and adapted to be driven by one ofsaid bodies, a hollow shaft mounted on said support with the axisthereof substantially parallel to the axis of said first cone pulley, ahollow cone pulley, bearing means rotatably mounting said hollow conepulley about said hollow shaft, a belt connecting said cone pulleys, adrive shaft rotatably mounted in said hollow shaft and projectingtherefrom at one end into said hollow cone pulley. a spur gear securedto said one end of said drive shaft, internally toothed ring geardisposed within said hollow cone pulley substantially in the planedefined by said spur gear, an end plate mounted on the end of saidhollow cone pulley adjacent to said ring gear, a planet carrier having ashaft, bearing means in said end plate rotatably mounting said shaft ofsaid planet carrier coaxially of said drive shaft, said shaft of saidplanet carrier extending through said end plate, at least one planetgear rotatably mounted on said planet carrier in a position meshing withboth said ring gear and said spur gear, an electrical pickofi devicehaving an input shaft, means including a variable speed drive connectingsaid planet carrier shaft to said input shaft of said electricalpiclcoff, and a slip clutch forming part of the driving connection forlimiting the transmitted torque between said planet cafirrier shaft andsaid input shaft of said electrical pick- 0 12. Apparatus for indicatinga difference in angular position between two rotatable bodiescomprising, a support, a first cone pulley rotatably mounted on saidsupport and adapted to be driven by one of said bodies, a hollow shaftmounted on said support with the axis thereof substantially parallel tothe axis of said first cone pulley, a hollow cone pulley, bearing meansrotatably mounting said hollow cone pulley about said hollow shaft, abelt connecting said cone pulleys, a drive haft rotatably mounted insaid hollow shaft and projecting therefrom at one end into said hollowcone pulley, a spur gear secured to said one end of said drive shaft, aninternally toothed ring gear disposed within said hollow cc pulleysubstantially in the plane defined by said gear, an end plate mounted onthe end of said cone pulley adjacent to said ring gear, a planet havinga shaft, bearing means in said end plate re mounting said shaft of saidplanet carrier coaxially of said drive shaft, said shaft of said planetcarrier extending through said end plate, at least one planet rotatablymounted on said planet carrier in a pos ion meshing with both said ringgear and said spur an electrical piclrofi device having an input shaftincluding a variable speed drive connecting said carrier shaft to saidinput shaft of said electrical i a slip clutch forming part of thedriving connectior limiting the transmitted torque between said planetcar-- rier shaft and said input shaft of said electrical picked, andsaid slip clutch comprising a plurality engaged friction plates.

13. Apparatus for indicating a difference in angular position betweentwo rotatable bodies comprising, a support, a first cone pulleyrotatably mounted on said support and adapted to be driven by one ofsaid bodies,

a hollow-shaft mounted on said supportwith the axis thereofsubstantially parallel to the axis of said first cone pulley, a hollowcone pulley, bearing means rotatably mounting said hollow cone pulleyabout said'hollow shaft, a belt connectingsaid cone pulleys, a driveshaft rotatably mounted in said hollow shaft and projecting therefrom atone end into said hollow cone pulley, a spur gear secured to said oneend of said drive shaft, an ini ternally toothed ring gear disposedwithin said hollow cone pulley substantially in the plane defined bysaid spur gear, an end plate mountedon the end of said hollow conepulley adjacent to said ring gear, a planet carrier having a shaft,bearing means in said end plate rotatably mounting said shaft of saidplanet carrier coaxially of said drive shaft, said shaft of said planetcarrier extending V through said end plate, at least one planet gearrotatably mounted on said planet carrier in a position meshing with bothsaid ring gear and said spur gear, an electrical pickoif device havingan input shaft, a pulley cluster connested-to said planet carrier shaft,a pulley cluster connected to said input shaft of said electricalpickoff, and a belt connecting corresponding pulleys of said respectiveclusters, said belt being movable between corresponding pulleys of saidrespective clusters to vary the drive ratio therebetweenn 14. Apparatusfor indicating a diflference in angular position between two rotatablebodies comprising, a support, a first cone pulley rotatably mounted onsaid support and adapted to be driven by one of said bodies, a hollowshaft mounted on said support with the axis there of'substantiallyparallel tothe axis of said first cone pulley, a hollow cone pulley,bearing means rotatably mounting said 'hollow cone pulley about saidhollow shaft,

abelt connecting said cone'pulleys, a drive'shaft'rotat- I ably mountedin' said hollow shaft and projecting therefrom at one end'into saidhollow cone pulley, a spur gear secured to said one end of said driveshaft, an internally toothed ring gear disposed'within said hollow 'conepulley substantially in the plane defined by said spur gear, an endplate mounted on the end of said hollow cone pulley adjacent to saidring gear, a planet carrierhaving a shaft, bearing means in said endplate rotatably mounting said shaft of said planet carrier coaxially'ofsaid drive shaft, said shaft of said planet carrier extending throughsaid end plate,-at least one planet gear rotatably mounted on saidplanetcarn'er in a position'meshing with both said ring gear and saidspur gear/an elec 7 12 trical pickoff device having an input shaft, apulley cluster connected to said planet carrier shaft, a pulley clusterconnected to said input shafts of said electrical pickolf, a beltconnecting corresponding pulleys of said respective clusters, said beltbeing movable between corresponding pulleys of said respective clustersto vary the drive ratio therebetween, and a slip clutch connecting oneof said pulley clusters with the shaft therefor.

15. Apparatus for indicating a difierence in angul position between tworotatable bodies comprising, a support, a first cone pulley rotatablymounted on said support and adapted to be driven by one of said bodies,'a hollow shaft mounted on said support with the axis thereofsubstantially parallel to the axis of said first cone pulley, a hollowcone pulley, bearing means rotatably mount ing said hollow cone pulleyabout said hollow shaft, a belt connecting said cone pulleys, a driveshaft rotatably mounted in said hollow shaft and projecting therefrom 7at one end into said hollow cone pulley, a spur gear se-' cured to saidone end of said drive shaft, an internally toothed ring gear disposedwithin said hollow cone pulley substantially in the plane defined bysaid spur gear,-an end plate mounted on the end of said hollow conepulley adjacent to said ring gear, a planet carrier having a shaft,bearing means in said end plate rotatably mounting said shaft of saidplanet carrier coaxially of said drive shaft, said shaft'of said planetcarrier extending through said end plate, at least one planet gearrotatably mounted "on said planet carrier in a position meshing withboth References Cited in the file of this patent UNITED STATES PATENTSMaxson Feb. 10, 1931 2,346,047 Otto Apr. 4; 1944 Weiser Mar. 4, 1952

